(1) Field of the Invention
The present invention relates to a bulky or filmy oxide superconductor which is used for a magnetic coil portion of a magnetic levitated vehicle or particle accelerator or a circuit substrate of an electronic device or Josephson element.
(2) Description of the Prior Art
At the present, a metal type superconductor represented by Nb.sub.3 Ge or Nb.sub.3 Sn is practically utilized as the superconductor, but the critical temperature (Tc) of the superconductor of this type is about 23.2.degree. K. at highest.
However, it has recently been reported that the critical temperature of an oxide type superconductor composed of a mixture of a rare earth element, an alkaline earth metal element and copper oxide is much higher than the critical temperature of the metal type superconductor (for example, the group of the Department of Technology, Tokyo University, published in the physical Society of U.S.A. that the critical temperature of 90.degree. K. was attained), and it has become possible to use cheap liquefied nitrogen sufficiently as the cooling medium instead of expensive liquefied helium which is liquefied at a cryogenic temperature (4.2.degree. K.=-268.8.degree. C.). Therefore, the prospect of the utilization of this oxide type superconductor in various fields is brightened. After these presentations, investigations have been vigorously made to further elevate the critical temperature (Tc) of a bulky or filmy oxide type superconductor almost to a level of normal temperature in these utilization fields. However, an oxide superconductor having a sufficiently high critical temperature (Tc) has not yet been known.